The technique of eXcess eNvelope eNhancement (XNN®) for power amplifiers (PA) is a simplification of Envelope Tracking (ET), which is a solution for efficiency enhancement and power boost of power amplifiers, particularly for the low power WiFi and high power and low power WiMAX market applications, as well as for existing high power cellular applications and forthcoming cellular standards. Such solution is disclosed, for example in U.S. Pat. No. 6,831,519, in U.S. Pat. No. 6,437,641 and in US Patent Application No. 2004/0018821.
The Voltage Enhancement Circuit (VEC™) modulates the supply voltage of power amplifiers as part of the XNN® technology, disclosed in U.S. Pat. No. 6,437,641. Appropriate modulation of the supply voltage prevents saturation of power amplifiers while amplifying signals that exceed a pre-defined programmable threshold.
A MIMO system requires using of several power amplifiers, one for each transmitting path of the information signal. Conventional implementation of XNN® technology for this case requires using a VEC™ circuit for each replica of the signal. However, using several VEC™ circuits on one board might be expensive and area as well as power consuming. Therefore, a novel technique for reducing the number of VEC™ circuits required for the operation of a MIMO system is needed.
All the methods described above have not yet provided satisfactory solutions to the problem of efficiently providing power enhancement to several power amplifiers, arranged in a MIMO system.
It is therefore an object of the present invention to provide a method and circuitry for efficiently providing power enhancement to several power amplifiers, arranged in a MIMO system.
It is another object of the present invention to provide a method and circuitry for efficiently providing power enhancement to power amplifiers, arranged in a MIMO system.
It is another object of the present invention to provide a method and circuitry for efficiently providing power enhancement to power amplifiers, arranged in a MIMO system, while reducing heat dissipation.
It is a further object of the present invention to provide a method and circuitry for efficiently providing power enhancement to power amplifiers, arranged in a MIMO system, while reducing the output signal distortion.
It is yet an object of the present invention to provide a method and circuitry for efficiently providing power enhancement to power amplifiers, arranged in a MIMO system, while reducing the area, costs and power dissipation of the enhancement circuitry.
Other objects and advantages of the invention will become apparent as the description proceeds.